1. Field of the Invention
This invention relates to stainless steels which are economical and superior in cold workability, corrosion resistance and hot workability and are utilized for such objects as screws.
2. Description of the Prior Art
Such austenitic stainless steels as 17.5 Cr-13 Ni steel (SUS 305J.sub.1), 18 Cr-9.5 Ni-3 Cu steel (SUSXM7) have been used for stainless steel wires for manufacturing screws. These steels, however, are expensive due to their high nickel content, although they are superior in cold workability, corrosion resistance and hot workability. Recently 17 Cr-6 Ni-6 Mn-2 Cu steel (SUSXM1) and 15.5 Cr-7.8 Ni-4 Mn-3 Cu steel, which contain less nickel, have been developed to lower the price of steel. In place of nickel, these steels contain 4-6% manganese (which forms an austenitic phase), and some of these steels have already been in actual use. The cold workability of these steels, which have tensile strengths of from 54-56 kg/mm.sup.2, however, is inferior to that of SUSXM7. The corrosion resistance of these steels is not sufficient, either. Therefore, the development of austenitic stainless steels which possess superior cold workability and corrosion resistance (comparable to that of SUSXM7) and are also economical has been sought after.
Superior austenitic stainless steels have been developed by the present inventors as a result of research on the effects of carbon and the silicon, the relationship of nickel and manganese, and alloying balance of such elements as chromium, nickel, manganese, carbon, silicon, nitrogen, and copper in relation to cold workability, corrosion resistance and hot workability of austenitic stainless steels.